Connection Diagrams

Functional Description

The

’AC/’ACT257

is

quad

2-input

multiplexer

with

TRI-STATE outputs. It selects four bits of data from two

sources under control of a Common Data Select input. When

the Select input is LOW, the I

Select is HIGH, the I

selected inputs appears at the outputs in true (noninverted)

form. The device is the logic implementation of a 4-pole,

2-position switch where the position of the switch is deter-

mined by the logic levels supplied to the Select input. The

logic equations for the outputs are shown below:

Z

Z

Z

Z

When the Output Enable (OE) is HIGH, the outputs are

forced to a high impedance state. If the outputs are tied to-

gether, all but one device must be in the high impedance

state to avoid high currents that would exceed the maximum

ratings. Designers should ensure the Output Enable signals

to TRI-STATE devices whose outputs are tied together are

designed so there is no overlap.

Truth Table

Output

Select

Data

Outputs

Enable

Input

Inputs

OE

SI

0

I

1

Z

HX

X

X

Z

LH

X

L

L

LH

X

H

H

LL

L

X

L

LL

H

X

H

H = HIGH Voltage Level

L = LOW Voltage Level

X = Immaterial

Z = High Impedance

Logic Diagram

Pin Assignment for

DIP and Flatpak

DS100286-3

Pin Assignment for LCC

DS100286-4

DS100286-5

Please note that this diagram is provided only for the understanding of logic operations and should not be used to estimate propagation delays.

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